Self-arranging coating

ABSTRACT

The invention relates to a coating composition, to a formulation comprising said coating composition, to methods of coating surfaces with the coating composition, and to articles coated with the coating composition. The coating composition is based on a complex of polyelectrolytes and oppositely charged surfactants. The surfactants contain fluorine bonded covalently to carbon atoms. The coating material imparts oleophobic and/or hydrophobic properties to various surfaces. The degree of hydrophobicity and other properties such as, for instance, gas or moisture permeation can be adjusted over a wide range. Through the use of additives, the coating can be executed as a permanent or temporary coating. The readily variable profile of properties, the uncomplicated application, and the low coat thickness result in a wide scope for application as, for example, an antisoiling, antigraffiti or antiadhesion coating.

DESCRIPTION

The invention relates to a coating composition, to a formulationcomprising said coating composition, to methods of coating surfaces withthe coating composition, and to articles coated with the coatingcomposition. The coating composition is based on a complex ofpolyelectrolytes and oppositely charged surfactants. The surfactantscontain fluorine bonded covalently to carbon atoms. The coating materialimparts oleophobic and/or hydrophobic properties to various surfaces.The degree of hydrophobicity and other properties such as, for instance,gas or moisture permeation can be adjusted over a wide range. Throughthe use of additives, the coating can be executed an a permanent ortemporary coating. The readily variable profile of properties, theuncomplicated application, and the low coat thickness result in a widescope for application as, for example, an antisoiling, antigraffiti orantiadhesion coating.

In the field of coating techniques, there exists a virtually innumerablenumber of different coating materials, each for very specificapplications. In some cases a combination of polyelectrolytes andsurfactants has been described.

DE 42 20 975 A1 describes oleophobic and/or permanent hydrophobicfinishing for polymeric surfaces with a thin film. The film is formedfrom at least one layer of a water-soluble polycation and/or of acationic synthetic resain. To further improve the oleophobic and/orpermanently hydrophobic properties, the film may further comprise along-chain surfactant or an alkyl-substituted polyanion. In the processdescribed, the surface is first treated with a polycation solution andthen treated, if desired, with an alkyl-substituted polyanion as secondcomponent or with a long-chain surfactant. Therefore, at least twodifferent operations are required for coating. Furthermore, aprerequisite for application of the process is that the surface to becoated possesses a negative zeta potential.

This layer-by-layer construction by adsorption from aqueous solution hasalready been used for many years for scientific purposes and isdescribed in a review by Decher (Science 277 (1997), 1232-1237).

International Patent Application Wo 96/11981 describes afluorocarbon-containing additive which is applied subsequently topainted substrates and protects them against soiling or makes themeasier to clean. These additives are based on discrete oligomerscomprising a polyfunctional oligomeric core to which fluorinated alkylchains are bonded covalently. The dirt repellency feature is achievedthrough the fluorinated alkyl chains, while adhesion to the paint isinduced by the functionalized core. This type of protection by means ofadditives is strongly limited to well-defined, i.e. dust-free, paintedsurfaces. Furthermore, reaction times of from 6 hours to two weeks arenecessary for preparing the fluorinated additives.

U.S. Pat. No. 5,330,788 describes a temporary coating for surfaces,developed in particular for protecting automobiles in transit. Thecoating is based on a film-forming acrylic acid polymer, a nonionicacetylenically unsaturated surfactant, if desired, a phosphate estersurfactant, and a base for neutralization. The coating material can beremoved rapidly in contact with a special alkaline aqueous medium, whichis likewise described in the patent. Extremely disadvantageous are,apparently, the long drying times for the coating, which are stated asbeing “overnight” or 24 hours. Since the principal component, thepolyacrylic acid, is a polyelectrolyte which finds application as asuper-absorbent (used, for example, in diapers and to improve the waterretention capacity of arid soils), it cannot be assumed that thesedrying times, which are unreasonably long from an economic standpoint,might be substantially reduced.

U.S. Pat. No. 5,387,434 describes an antigraffiti composition whoseprotective action derives from sodium silicate. Since this is soluble inwater, the interface between substrate and environment must be madehydrophobic. This is achieved by means of latex, silicones, or waxes.Particularly suitable are microcrystalline wax emulsions which arestabilized by sodium lignin-sulfonate. Graffiti removal requireshigh-pressure steam jets with a pressure of 100 psi, and temperatures ofup to 90° C. Consequently, this process is suitable only for veryspecific substrates which permit these conditions without damage. Nostatement concerning the drying time of the coating can be found in thepatent. However, it must be assumed that the crosslinking of thesilicate requires several hours to days. Furthermore, it is likely thatdrying, which is retarded as a result of the added wax, will likewisetake at least one day under dry conditions.

DE 36 30 520 C1 describes a process for protecting applications of colorto surfaces of natural and synthetic stone. The process consists of twosteps: first, an inorganic impregnation is applied, which is notspecified in any great detail. This is followed by the application of acolor-accepting, detachable, wax-like coating which can be removed bymeans of high-pressure hot water. Owing to the fact that it necessitatesat least two different operations, this process is very time-consuming.In the case of typical inorganic impregnations, from at least one tothree days are necessary given dry weather. Furthermore, this process isapplicable only to a very limited number of specific substrates.

European Patent Application EP 0 695 772 A1 describes a class offluorine-containing polyethers which are applied to masonry where theycrosslink and form an impermeable antigraffiti film. The synthesis ofthe crosslinkable substances, however, is time-consuming and costly, andthe raw material applied requires a drying time of 48 hours on themasonry in order to crosslink sufficiently. Furthermore, the field ofuse is limited to the coating of masonry.

Available on the market there is a surface protection is system from thecompany PSS (Protective Surface System) which is based or apolysaccharide mixture. According to an examination certificate from theGerman Federal Institute of Materials Research (Report No.3.14.3441-91), effective protection against graffiti with the system PSS20 requires three coats with drying times of from 24 to 72 hours in eachcase. Thus from 3 to 9 days are necessary for the application of theprotective coat.

All of the abovementioned coating processes are characterized by aclosely limited field of use and, in some cases, by drying times ofseveral days for the protective coats.

DE-A-44 28 641 describes mesomorphic complexes comprising anionicpolyelectrolytes, cationic polyelectrolytes and/or polyampholytes, andcationic, anionic, nonionic and/or amphoteric surfactants. As aconsequence of the mesomorphic structure, generally improved materialproperties, such as increased mechanical strength, for example, areexpected. The materials constructed of these amorphous or mesomorphicpolyelectrolytes, such as films or membranes, include as an essentialcomponent surfactants having a hydrocarbon framework. Coatings withlow-energy surfaces, however, cannot be produced using the fluorine-freecomplexes described therein.

Antonietti et al. (Adv. Mater. 8 (1996), 41-45) and Lochhaas et al.(Polyelectrolyte-surfactant complexes with fluorinated surfactants: Anew type of material for coatings (3^(rd) conference in the series: HighPerformance Coating Materials, Fluorine in Coatings II, Feb. 24-26,1997, Munich, Germany) describe complexes comprising cationicpolyelectrolytes and anionic fluorinated surfactants. Cationicpolyelectrolyte components disclosed include polyacrylic acid,polymethacrylic acid, and poly(diallyldimethylammonium chloride). Oncontact with moisture these complexes have a very high propensity toabsorb water; they swell rapidly and in doing so become soft togelatinous. This leads to a considerable deterioration in the mechanicalproperties, so rendering them unsuitable for practical applications ascoating material.

It is an object of the present invention to develop a coating materialin which at least some of the disadvantages of the prior art areeliminated. In particular, the coating material should be applicable bysimple methods to any desired surfaces and should produce a low-energysurface even when small amounts are used. Furthermore, the coatingmaterial should be highly stable to a water-containing environment.

This object is achieved through the provision of a coating materialbased on a complex which comprises at least one nonhygroscopicpolyelectrolyte and at least one oppositely charged, fluorinatedsurfactant.

The coating material of the invention surprisingly allows anaccumulation of fluorinated organic groups—alkyl chains, for example—atits surface, so that the oleophobic—or hydrophobic—properties of thecoated surface are improved. Through the combination of nonhygroscopicpolyelectrolyte and fluorinated ionic surfactant a highly ordered,mechanically stable complex is formed which both adheres to almost anysubstrate and forms a highly fluorinate, low-energy surface. Sufficientadhesion and the formation of low-energy surfaces are inherentlycontradictory principles, which can surprisingly be unified in onematerial by the novel combination of nonhygroscopic polyelectrolyte andfluoro surfactant.

The complex of the invention may comprise a cationic polyelectrolyte andan anionic surfactant, or an anionic polyelectrolyte and a cationicsurfactant. It is preferred to use cationic polyelectrolytes and anionicsurfactants.

The stoichiometry of the complex, based on the charges ofpolyelectrolyte and surfactant, is preferably such that there isessentially charge compensation in respect of the polyelectrolyte on theone side and surfactant on the other. Advantageously, therefore, thestoichiometry of the complex, based on the charges of polyelectrolyteand surfactant, is from about 1.5:1 to 1:1.5, with particular preferencefrom about 1.3:1 to 1:1.3, and most preferably about 1:1.

In addition, the complex preferably has a mesomorphic structure, as maybe determined by measuring the small-angle X-ray scattering. It isfurther preferable that the complexes of the invention possess nocrystallinity, as can be determined by measuring the wide-angle X-rayscattering.

The complexes of the invention are obtainable by adding an aqueoussolution of the polyelectrolyte to an aqueous solution of thefluorinated surfactant and isolating the resultant precipitate, whichforms spontaneously. Both when adding a cationic polyelectrolyte inaqueous solution to an aqueous solution of the anionic fluorinatedsurfactant, and when adding an anionic polyelectrolyte to a cationicfluorinated surfactant, the complex preferred in accordance with theinvention is formed with a stoichiometry of about 1:1, based on thecharges of polyelectrolyte and surfactant. Moreover, the formation ofthis preferred complex is favored by working at an elevated temperatureof at least 40° C., with particular preference from 50 to 90° C. In theconverse case—the addition of a surfactant solution to thepolyelectrolyte solution—it is not unusual for there to be considerabledeviations from the preferred stoichiometry, which in certain instancesmay result in an unwanted sharp increase in the hygroscopicity.

The resultant novel supramolecular polymer complex precipitate may bedissolved in polar organic solvents. This is surprising, since polymericmaterials having a high fluorine content are usually of extremely lowsolubility or else completely insoluble. When this complex solution isapplied to a surface and the solvent is evaporated, a thin, usuallytransparent film of the complex material is formed on the surface. Ithas been found that the surface energy after coating with the complexmaterials of the invention was lower in all cases than prior to coating.A consequence of this is reduced adhesion of impurities on the surface.This effect was found on a large number of different surfaces, examplesbeing glass, stone, wood, paper, metal, plastics, natural materials suchas cotton fibers, for instance, and on painted surfaces as well; inother words, the effect is independent of the type of substrate and isaccompanied by good coating adhesion.

A further surprising finding has been that the complexes of theinvention are readily emulsifiable with nonionic surfactants, preferablynonionic fluorinated surfactants. In this way, the complexes may also beprocessed with an aqueous carrier material and hence applied in aparticularly environment-friendly way.

The present invention therefore further provides a complex comprisingpolyelectrolyte and ionic fluorinated surfactant, said complex furthercomprising at least one nonionic surfactant, preferably a nonionicfluorinated surfactant. The proportion of the nonionic surfactant may bevaried over a wide range depending on the nature of the application andmay, for example, be up to 200% (w/w) based on the weight of thecomplex.

By varying the proportion of emulsifier, i.e., nonionic surfactant, itis possible to control the permanence of the coating. For theapplication of permanent coatings, the proportion of the nonionicsurfactant should be up to not more than 20%, preferably up to 10% and,with particular preference, up to 5%, based in each case on the weightof the complex. For temporary coatings, proportions of the nonionicsurfactant of from 20 to 200% and, in particular, from 50 to 80%, basedon the weight of the complex, are preferred. With a high proportion ofemulsifier, the coating may be washed off using customary domesticsurfactant solutions. This is of great interest in particular for thetemporary intransit coating of, say, automobiles.

It has been found, furthermore, that the gas permeability and waterabsorption capacity may both be varied widely by means of appropriatecombinations of polyelectrolyte and surfactant. This is of greatimportance since with many coatings, such as antigraffiti coats, forexample, it is necessary not to seal the surfaces, in order to preventthe formation of mold and fungus.

The complex compounds of the invention can be prepared easily andquickly, from aqueous solution, for example.

They can be processed both as solutions and as aqueous emulsions to formthin films on any desired surfaces. For very low expenditure ofmaterial, these films greatly reduce the surface energy, and so can beused almost universally wherever surfaces having Teflon-like propertiesare required or desired.

Owing to the low coat thicknesses required to reduce the surface energy,the ease of preparation, and the short drying times, the coating is verycost-effective per unit area. The drying times of the films may bereduced to a few minutes or hours. The coating permits elastic flexingof the coated articles. The film coatings are preferably transparent andare impossible or difficult to perceive under light which is incident,for example, at an oblique angle. The breathability, i.e., thepermeability to gases and water vapor, and also water absorption, can beadjusted within wide limits.

The coating of surfaces with the polyelectrolyte-fluoro surfactantcomplexes of the invention is always judicious when the aim is to reducenatural or artificial soiling. For this purpose the surface is coatedwith a thin film. Irrespective of the nature of the surface, the surfaceenergy is reduced as a result of the coating. The coating permitselastic flexing of the coated article without chipping or flaking. Thefilms possess long-term stability at temperatures of up to 100° C.Depending on the complex used, temperature stabilities of from 120 up to230° C. may even be attained.

With the exception of highly hygroscopic polyelectrolytes such aspolyacrylic acid, polymethacrylic acid and poly(diallyldimethylammoniumchloride), and salts thereof, any desired combinations ofpolyelectrolytes and fluorinated ionic surfactants are suitable. Whenusing nonhygroscopic polyelectrolytes of the invention, the complexesobtained have a low water absorption of preferably not more than 5%(w/w), with particular preference not more than 4.5% (w/w), and mostpreferably not more than 4% (w/w), based on the weight of the complex,at 20° C. and 100% relative atmospheric humidity.

Polyelectrolytes are substances containing two or more positive ornegative charge carriers. A preferred class of cationic polyelectrolytesare polymers containing preferably at least 20% of one or more of thefollowing monomer units, with the proviso that the resultantpolyelectrolyte is a nonhygroscopic polyelectrolyte within the meaningof the present invention:

ethylenically unsaturated monomers which carry positively chargednitrogen groups, e.g., quaternary ammonium groups or N-substitutedheteroaromatic groups, said monomers being in the form either of salts,as obtained by reacting basic amino functions with mineral acids, e.g.,hydrochloric acid, sulfuric acid or nitric acid, or in quaternized form(e.g., by reaction with dialkyl sulfates such as dimethyl sulfate,diethyl sulfate, etc., alkyl chlorides such as methyl chloride, ethylchloride, etc., or benzyl chloride), examples being dimethylaminoethylacrylate hydrochloride, diallyldimethylammonium chloride,dimethylaminoethyl acrylate methosulface,di-methylaminopropylmethacrylamide methochloride,di-methylaminopropylmethacrylamide methosulfate, vinylpyridinium salts,and 1-vinylimidazolium salts.

In addition to the cationic monomer units, the cationic polyelectrolytemay if desired contain one or more nonionic monomers in an amount, forexample, of up to 80 mol %. The presence of nonionic monomers isnecessary in some instances, as in the case ofpoly(diallyldimethylammonium chloride), for example, in order to reducethe hygroscopicity.

Examples of suitable nonionic monomers are C₁ to C₂₀ alkyl esters andhydroxyalkyl esters, and especially amides and N-substituted amides, ofmonoethylenically unsaturated C₃ to C₁₀ monocarboxylic acids or C₄ to C₈dicarboxylic acids, e.g., acrylamide, methacrylamide, N-alkylacrylamidesor N,N-dialkylacrylamides having in each case 1 to 18 carbon atoms inthe alkyl group, such as N-methylacrylamide, N,N-dimethylacrylamide,N-tert-butylacrylamide or N-octadecylacrylamide, N-methylhexylmaleimide,N-decylmaleimide, dimethylaminopropylmethacrylamide oracrylamidoglycolic acid, and also alkylaminoalkyl (meth)acrylates,examples being di-methylaminoethyl acrylate, dimethylaminoethylmethacrylate, ethylaminoechyl acrylate, diethylaminoethyl methacrylate,dimethylaminopropyl acrylate and di-methylaminopropyl methacrylate, andalso vinyl esters, examples being vinyl formate, vinyl acetate and vinylpropionate, which after polymerization may also be present in hydrolyzedform, and also N-vinyl compounds, examples being N-vinylpyrrolidone,N-vinylcaprolactam, N-vinylformamide, N-vinyl-N-methylformamide,1-vinylimidazole, 1vinyl-2-methylimidazole, and N-methylvinylacetamide.

An example of cationic polyelectrolytes composed of cationic andnonionic monomers is as follows:

copolymers of dialkenyldialkylanmonium salts, e.g.,diallyldimethylammonium chloride, with nonionic monomers, e.g.,N-methylvinylacetamide, in which the proportion of nonionic monomer ispreferably at least 20 mol %.

Further preferred classes of cationic polyelectrolytes are thefollowing:

polyethyleneimines and alkyl-substituted polyethyleneimines, e.g.,poly(ethyleneimine-co-N-docosylethylimine);

ionenes, i.e., polymers having two or more quaternary ammonium groupsand formed, for example, by reacting di-tertiary amines withα,ω-dihaloalkenes, e.g., 6,3-ionene, and

polysaccharides containing cationic groups, especially β-glycosidicallylinked polysaccharidea, such as chitosan, for instance.

To prepare the complexes of the invention, said cationicpolyelectrolytes can be used in base form, partially neutralized ortully neutralized.

In addition, anionic polyelectrolytes are also suitable for the methodof the invention. A preferred class of such anionic polyelectrolytes arepolymers containing preferably at least 20 mol % of one or more of thefollowing monomer units, with the proviso that the resultantpolyelectrolyte is a nonhygroscopic polyelectrolyte within the meaningof the present invention:

ethylenically unsaturated carboxylic acids and their salts andderivatives, e.g., C₃ to c₁₀ mono-carboxylic acids, their alkali metaland/or ammonium salts, examples being dimethylacrylic acid orethylacrylic acid, C₄ to C₈ dicarboxylic acids, their monoesters,anhydrides, alkali metal salts and/or ammonium salts, e.g., maleic acid,fumaric acid, itaconic acid, mesaconic acid, methylenemalonic acid,citraconic acid, maleic anhydride, itaconic anhydride or methylmalonicanhydride;

ethylenically unsaturated monomers containing sulfonic acid groups,examples being allylsulfonic acid, styrenesulfonic acid, vinylsulfonicacid, 3-sulfopropyl acrylate, and 3-sulfopropyl methacrylate,

monoethylenically unsaturated monomers containing phosphinic, phosphonicor phosphoric acid groups, e.g., vinylphosphonic acid, allylphosphonicacid, or acrylamidomethylpropanephosphonic acid.

If desired, these anionic polymers may contain one or more of theabovementioned nonionic monomers in a proportion, for example, of up to80 mol %. The use of copolymers comprising anionic and nonionic monomersis preferred for some of the anionic monomers in order to reduce thehygroscopicity.

A further preferred class of anionic polyelectrolytes arepolyaaccharides containing anionic groups.

The anionic polyelectrolytes can be used in the acid form, partiallyneutralized or fully neutralized.

Ionic fluorinated surfactants are substances which contain at least onefluorine atom attached to a carbon atom, preferably at least one —CF₂group and/or CF₃ group, and at least one charge carrier.

Anionic fluorinated surfactants comprise at least onefluorine-containing hydrophobic group and at least one negative chargecarrier. Examples of such compounds are fluorinated carboxylic acids andtheir salts with organic or inorganic cations, fluorinated sulfonicacids and their salts with organic or inorganic cations, fluorinatedorganic sulfuric acids and their salts with organic or inorganiccations, and fluorinated phosphinic, phosphonic or organ-phosphoricacids and their salts with organic or inorganic cations.

Among these classes of compound, preference is given to the following;

perfluorocarboxylic acids and their preferably water-soluble salts, suchas perfluoroalkanoic acids, e.g., in particular, perfluoroalkanoic acidsof the formula CF₃(CF₂)_(n)—COOH, where n is preferably≧7;

partially fluorinated carboxylic acids and carboxylic acid salts, suchas partially fluorinated alkanoic acids, partially fluorinated alkenoicacids, perfluoroalkoxyalkanoic acids, perfluoroalkylethyleneoxyalkanoicacids, perfluoroalkoxybenzoic acids, and partially fluorinatedcarboxylic acids containing sulfide, sulfone, carboxamide, hydroxyl, oxoand/or ether groups, and salts of such acids; e.g., lithium 3-[(1H, 1H,2H, 2H-fluoroalkyl) thio]propionate, Zonyl FSA®, Du Pont;

perfluorosulfonic acids and their preferably water-soluble salts, suchas perfluoroalkanesulfonic acids of the formula CF₃(CF₂)_(m)—SO₃H, wherem≧1;

partially fluorinated sulfonic acids and their preferably water-solublesalts, such as partially fluorinated alkanesulfonic acids, e.g.,perfluoroalkylethaniesulfonic acids, perfluoropropylalkanesulfonicacids, partially fluorinated arylsulfonic acids, e.g.,perfluoroalkylbenzenesulfonic acids, perfluoroalkoxybenzenesulfonicacids, perfluoroacylbenzenesulfonic acids, partially fluorinatedalkenesulfonic acids, and also partially fluorinated sulfonic acidscontaining sulfide, carboxamide, hydroxyl, oxo and/or ether groups,fluorinated sulfo esters, e.g., sulfosuccinic esters, perfluoroalkylsulfopropionates, perfluoroalkyl sulfobutyrates and salts thereof; e.g.perfluoroalkylethylsulfonic acid ammonium salt, Zonyl TBS® Du Pont;sodium [succinic acid diperfluoroalkylethyl diester 2-sultonate],Fluowet SB®, Hoechst;

fluorinated organic sulfuric acids and their salts, such asperfluoroalkylated methyl sulfates, fluorinatedsulfatopoly(oxyethylene), perfluoropropoxylated sulfates, and saltsthereof;

fluorinated phosphinic and phosphonic acids and their preferablywater-soluble salts, e.g., Fluowet PL80®, Hoechst;

fluorinated organic phosphoric acids and their salts, such asperfluoroalkylethanephosphoric acids, mono- andbis(fluoroalkyl)phosphoric acids, perfluoroalkylphosphoric acids,fluorinated alkene-phosphoric acids, fluorinated phosphate alkyl esters,e.g., phosphoric acid perfluoroalkyl ester ammonium salt, Zonyl FSE® andZonyl FSP®, Du Pont.

Cationic surfactants are also suitable for the method of the invention.Preferred classes of such compounds are as follows:

fluorinated amines and ammonium salts, such as fluoroalkylammoniumsalts, which may if desired contain carboxamide, sulfonamide, sulfide,ester and/or hydroxyl groups, or heterocyclic nitrogen compounds, e.g.,perfluoroalkylethyltrialkylammonium methosulfate, Hoe-L-3658-1, Hoechst.

Examples of nonionic surfactants, especially fluorinated surfactants,are compounds containing one or more nonionic hydrophilic groups and oneor more fluorine-containing hydrophobic groups. Preferred examples ofsuch compounds are fluorinated alcohols, examples being those containingone or more oxyethylene or oxypropylene groups, fluorinated polyethers,fluorinated polyhydric alcohols, oxyalkylated perfluorophenols,perfluoroalkyl-2-ethanethiol derivatives, and also compounds containingcarboxamide or sulfonamide groups.

Further judicious ionic fluorinated surfactants that can be used toprepare the complexes, and nonionic fluorinated surfactants that can beused as emulsifiers to prepare aqueous emulsions, are described in thebook by Erik Kissa (Fluorinated Surfactants, Surfactant Science SeriesVol. 50, Marcel Dekker, Inc., New York, 1994)

Complexes of the invention further comprising a nonionic surfactant arepreferably prepared by adding the particular desired proportion ofnonionic surfactant to a complex comprising polyelectrolyte andfluorinated ionic surfactant.

The present invention further provides a formulation comprising acomplex of the invention, comprising polyelectrolyte and ionicfluorinated surfactant, in solution in a polar organic solvent. Saidformulation comprises the complex preferably in a proportion of from 0.1to 30% (w/w), with particular preference from 0.5 to 10% (w/w), and mostpreferably from 1 to 5% (w/w), based on the weight of the formulation.The solvent is preferably a volatile and largely nontoxic organicsolvent, examples being methanol, ethanol, acetone, ethyl acetate, andmixtures thereof.

The present invention additionally provides a formulation comprising acomplex of the invention, comprising polyelectrolyte and ionicfluorinated surfactant, and preferably nonionic surfactant, in emulsionin an aqueous solvent. The complex is present preferably in a proportionof from 0.1 to 30% (w/w), with particular preference from 0.5 to 10%(w/w), and most preferably from 1 to 5% (w/w), based on the weight ofthe emulsion. The emulsion of the invention is, surprisingly, stable at20° C. for at least two weeks.

The emulsion of the invention is obtainable by adding the particulardesired amount of a nonionic surfactant to a complex comprisingpolyelectrolyte and ionic fluorinated surfactant, converting thismixture into a substantially homogeneous mixture, and diluting thatmixture with water, preferably in portions, so as to obtain an aqueousemulsion.

The complexes of the invention, and the complex-containing compositions,might be used to coat surfaces. Exemplary applications are asantisoiling compositions, especially antigraffiti compositions, asprotective compositions for vehicles in transit, e.g., automobiles ormachines, as anti-icing protection, especially for civilian or militaryair travel, as marine antifouling coatings, as release agents andlubricants, in the production, for example, of tiles, bricks orconstruction shuttering, as compositions for impregnating textiles,e.g., cotton with GoreTex properties, and carpeting, and as a membrane,e.g., as a gas separation membrane.

The invention further provides a method of coating a surface, in which aformulation of the invention is applied to said surface and allowed todry. This coating operation may—where necessary—also be repeated, usingdifferent complexes in each case if desired. Application may be madefrom an organic solution or from an aqueous emulsion. The drying timefor organic solutions is preferably not more than 1 hour, withparticular preference from a few seconds to a few minutes. The dryingtime for aqueous emulsions is preferably not more than 6 hours, withparticular preference not more than 3 hours. The coating composition maybe applied discontinuously or continuously by means of customarytechniques such as, for instance, spraying, flow coating, dipping, ormechanical application, e.g., roller application. The thickness of thecoating is preferably from 0.1 μm to 1 mm, with particular preferencefrom 1 to 10 μm.

The present invention provides, further still, an article coated atleast in part with a coating comprising a complex of the inventioncomprising polyelectrolyte and fluorinated ionic surfactant. The coatedsurface preferably has an energy of less than 20 mN/m. The coating ispreferably substantially transparent, ie., transparent to visible light.Further, the coating is preferably stable to contact with awater-containing atmosphere; that is, it does not tend towardsignificant swelling. Furthermore, the coating is preferably stable upto a temperature of 100° C. Depending on what is required, the coatingmay be permanent or temporary, permeable to air and/or moisture, orimpermeable to air and/or moisture.

One advantage of the coatings of the invention is that at their surfacefacing the surroundings they have a heightened fluorine content ascompared with the interior of the coating, a fact which contributes toreducing the surface energy. Furthermore, they possess preferably acontact angle hysteresis of between 5° and 20°. In addition, thecoatings of the invention exhibit low water absorption, preferably notmore than 5% (w/w), with particular preference not more than 4.5% (w/w),and most preferably not more than 4% (w/w), based on the weight of thecoating, at 20° C. and 100% relative atmospheric humidity.

The invention is further illustrated by the following figures andexample. In the figures,

FIG. 1 shows the fracture edge of the film of a complex of theinvention, imaged in the scanning electron microscope (top) and in afluorine-specific EDX analysis (bottom), and

FIGS. 2 and 3 show wide-angle X-ray diffractograms ofpolyelectrolyte-fluorosurfactant complexes.

EXAMPLES

1. Preparation of Complexes

The drying times stated in the examples are 12 h in many cases. Theywere chosen so as to be long enough to allow precise determination ofthe yields. For commercial purposes, short drying times of approximately30 minutes, or no drying times, are sufficient. The complexes can alsobe used further without drying under reduced pressure.

1.1 Complexes of Poly(diallyldimethylammonium)

None of the complexes containing poly(diallyldimethylammonium) aspolyelectrolyte can be used as a coating material since in the presenceof moisture the water absorption is so high that there is severeswelling. Since very different surfactants were tested, the swelling maybe attributed to the polyelectrolyte. They are listed here in order toshow that they are markedly inferior to the complexes of the invention.Similar results are found with complexes containing polyacrylic orpolymethacrylic acid as polyelectrolyte.

1.1.1 Poly(diallyldimethylammonium)-Fluowet SB®

18 g (28% w/w, 5.5 mmol, 1.1 eq) of Fluowet SB® are introduced in 150 mlof deionized water (0.037 M). A solution of 0.81 g (5 mmol, 1 eq) ofpoly(diallyldimethylammonium chloride) in 50 ml of deionized water (1.6%w/w) is added dropwise (about 1 drop per second) with stirring at roomtemperature. Using a Büchner funnel, the precipitate is filtered offimmediately then washed (3 times 20 ml of water conditioned to 60° C.)and dried in a vacuum drying cabinet at 30° C. and 0.1 mbar for 12 h.The yield is 4.5 g (88% of theory).

A poly(diallyldimethylammonium)-Fluowet PL80® complex is preparedanalogously. The yield is 87% of theory.

1.1.2 Poly(diallyldimethylammonium)-Zonyl FSA®

4.0 g (25% w/w) of Zonyl FSA® are dissolved in 150 ml of deionizedwater. The solution is adjusted to a pH of 9 using aqueous sodiumhydroxide solution (10% w/w). A solution of 0.1 g ofpoly(diallyldimethylammonium chloride) (0.62 mmol) in 50 ml of deionizedwater is added slowly (1 drop per second) with stirring at 50° C.Subsequently, the pH is adjusted to 3 using hydrochloric acid (10%strength). A fine white precipitate is produced which is filtered offusing a Büchner funnel, washed (with 3 times 20 ml of water conditionedat 60° C.) and dried in a vacuum drying cabinet at 30° C. and 0.1 mbar.The yield is 0.3 g (84% of theory, assuming 0.28 g ofC₆F₁₃CH₂CH₂SCH₂CH₂COOLi).

The following complexes are prepared analogously:

poly(diallyldimethylammonium)-Zonyl FSE® (90% yield)

poly(diallyldimethylammonium)-Zonyl FSP® (80% yield)

poly(diallyldimethylammonium)-Zonyl TBS® (84% yield)

poly(diallyldimethylammonium) n-perfluorobutanesulfonate (75% yield)

poly(diallyldimethylammonium) n-perfluorooctanesulfonate (86% yield)

1.1.3 Poly(diallyldimethylammonium) 1H,1H,2H,2H-perfluoroethylsulfonate

0.5 g (1.17 mmol, 1.6 eq) of 1H,1H,2H,2H-perfluoroethylsulfonic acid areintroduced in 50 ml of deionized water and the pH is adjusted to 7 usingaqueous sodium hydroxide solution (10% w/w). 0.17 g ofpoly(diallyldimethylammonium chloride) (1.06 mmol, 1.0 eq) in 50 ml ofdeionized water is added slowly (1 drop per second) with stirring atroom temperature. A fine white precipitate is produced which isimmediately filtered off using a Büchner funnel, washed (with 3 times 20ml of water conditioned at 60° C.) and dried in a vacuum drying cabinetat 30° C. and 0.1 mbar. The yield is 0.50 g (86% of theory).

1.2 Complexes of the Random Cationic CopolymerPoly-(diallyldimethylammonium)-co-N-methyl-N-vinyl-acetamide inDifferent Charge Density with Perfluorinated Carboxylic Acids

The following series of copolymers was prepared in order to investigatethe influence of charge density on the water absorption and the surfaceproperties.

1.1 eq of n-perfluorocarboxylic acid (F(CF₂)_(p)COOH) are introduced in100 ml of deionized water and the pH is adjusted to 9 using aqueoussodium hydroxide solution (10% w/w). A solution of 1.0 eq of a randomcopolymer of diallyldimethylammonium chloride (DADMAC, 1 eq) andN-methyl-N-vinylacetamide (NMVA) in 50 ml of deionized water is addedslowly (1 drop per second) with stirring at 60° C. (or 80° C. for thelong-chain acid where p=17) Following adjustment of the pH to 3 usinghydrochloric acid (10% w/w), a white precipitate is produced. Thisprecipitate is filtered off immediately using a Büchner funnel, thenwashed (with 3 times 20 ml of water conditioned to 60° C.) and dried ina vacuum drying cabinet at 30° C. and 0.1 mbar.

TABLE 1 Perfluorocarboxylic acids used Perfluorocarboxylic Molecularweight acid g/mol Purity % F(CF₂)₆COOH 364.06 99 F(CF₂)₇COOH 414.07 96F(CF₂)₉COOH 514.08 98 F(CF₂)₁₇COOH 914.15 95

TABLE 2 PE-T ccmplexes Mass Mass Complex F(CF₂)_(p)COOH DADMAC/ Yield ing DADMAC/NMVA (m:n) - F(CF₂)_(p)COO in g NMVA in g (% of theory)DADMAC/NMVA (25:75) - F(CF₂)₇COO 0.31 0.30 0.32 (59) DADMAC/NMVA(25:75) - F(CF₂)₉COO 0.38 0.30 0.43 (71) DADMAC/NMVA (25:75) -F(CF₂)₁₇COO 0 69 0.30 0.76 (87) DADMAC/NMVA (47:53) - F(CF₂)₇COO 0.520.30 0.45 (63) DADMAC/NMVA (47:53) - F(CF₂)₉COO 0.63 0.30 0.62 (75)DADMAC/NMVA (47:53) - F(CF₂)₁₇COO 1.16 0.30 1.16 (92) DADMAC/NMVA(65:35) - F(CF₂)₇COO 0.66 0.30 0.60 (72) DADMAC/NMVA (65:35) -F(CF₂)₉COO 0.80 0.30 0.83 (86) DADMAC/NMVA (65:35) - F(CF₂)₁₇COO 1.480.30 1.45 (95) DADMAC/NMVA (83:17) - F(CF₂)₇COO 0.78 0.30 0.97 (85)DADMAC/NMVA (83:17) - F(CF₂)₉COO 0.95 0.30 1.20 (89) DADMAC/NMVA(83:17) - F(CF₂)₁₇COO 1.75 0.30 1.97 (91) DADMAC/NMVA (100:0) -F(CF₂)₆COO 1.00 0.40 0.69 (57) DADMAC/NMVA (100:0) - F(CF₂)₇COO 1.000.34 0.88 (77) DADMAC/NMVA (100:0) - F(CF₂)₉COO 1.00 0.28 0.87 (79)DADMAC/NMVA (100:0) - F(CF₂)₁₇COO 1.00 0.17 0.97 (90)

1.3 Polyethyleneimine Perfluorooctanoate

54 g (130 mmol) of perfluorooctanoic acid (Fluka Chemie) are dissolvedin 500 ml of water at 50° C. A clear viscosity solution is formed. 100ml of aqueous polyethyleneimine solution (20° C.) are added dropwiseover 5 minutes with stirring. The solution contains 5.6 g (130 mmol) ofpolyethyleneimine (Aldrich Chemie, 50% by weight aqueous solution,branched, M_(n)≈70,000, M_(w)=750,000). A white precipitate is formedimmediately and care must be taken to ensure that the reaction solutionis mixed thoroughly. Since the mixture is very viscous, this is bestdone with a coarse stirrer mechanism (e.g., KPG stirrer at 600-700 rpm).Complexation is exothermic and there is a temperature rise of about 5°C. to 54-56° C. Following addition of the polyethyleneimine solution,stirring is continued for 5 minutes and the precipitate is immediatelyseparated from the aqueous phase using a fluted filter. The precipitateis dewatered in a drying cabinet at 50° C. and 10⁻¹ mbar for 12 h,mortared and sieved. The product is a fine white homogeneous powder witha virtually quantitative yield (59.2 g).

1.4 Poly(ethyleneimine-co-N-docosylethyleneimine) n-perfluorononanoate

0.5 g (0.99 mmol, 1.1 eq) of n-perfluorononanoic acid is dissolved in100 ml of deionized water. A solution of 0.08 g (88 mmol, 1.0 eq) ofpoly(ethyleneimine-co-N-docosylethyleneimine) in 100 ml of deionizedwater is added slowly (1 drop per second) with vigorous stirring at atemperature of 70° C. The pH of the polyelectrolyte solution wasadjusted beforehand to 2 using hydrochloric acid (10%). A whiteprecipitate is produced spontaneously, filtered off immediately andwashed with 200 ml of water at 70° C. The precipitate is dried at 30° C.and 0.1 mbar for 12 h. The yield is 0.29 g (55% of theory).

1.5 Complexes of Poly(N,N,N-trimethylammonium-3-propylacrylamide)

Poly(N,N,N-trimethylammonium-3-propylacrylamide) perfluorooctanoate

30 g (71.9 mmol) of perfluorooctanoic acid are dissolved in 1250 ml ofwater at 50° C. and the pH of the solution is adjusted to 6 usingaqueous sodium hydroxide solution (10%). 13.51 g (65.4 mmol) ofpoly-(N,N,N-trimethylammonium-3-propylacrylamide chloride) (StockhausenGmbH) are added dropwise to this solution with vigorous stirring over 5minutes. The clear surfactant solution becomes cloudy immediately.Following the addition of the polyelectrolyte, stirring is continued for5 minutes. The mixture is left to cool to room temperature and theaqueous phase is poured off. This leaves a transparent gelatinousresidue. This residue is washed with 500 ml of water at 60° C. and thendried at 50° C. and 10⁻¹ mbar for 12 h. The yield is 32.9 g (90% oftheory)

Poly(N,N,N-trimethylammonium-3-propylacrylamide)-Fluowet SB®

15 g (28% w/w, 4.6 mmol, 1.1 eq) of Fluowet SB® are introduced in 150 mlof deionized water. A solution of 0.86 g (4.2 mmol, 1 eq) ofpoly(trimethylammonium chloride propylacrylamide) in 50 ml of deionizedwater adjusted to a pH of 2-3 with hydrochloric acid (10% w/w) is addedslowly (1 drop per second) with stirring at room temperature. Aprecipitate is formed which is immediately filtered off with a Büchnerfunnel, then washed (with 3 times 20 ml of water conditioned at 60° C.)and dried in a vacuum drying cabinet at 30° C. and 0.1 mbar. The yieldis 4.3 g (=98% of theory).

1.6 Poly(acryloyloxyundecyltrimethylammonium)n-perfluorooctanoate

0.61 g (1.47 mmol, 1.1 eq) of n-perfluorooctanoic acid are introduced in100 ml of deionized water and the pH is adjusted to 9 using aqueoussodium hydroxide solution (10%). A solution of 0.43 g (1.35 mmol, 1.0eq) of poly(acryloyloxyundecyltrimethylammoniumn chloride in 100 ml ofdeionized water is added slowly at 30° C. A fine white precipitate formsspontaneously, and is filtered off immediately with a Büchner funnel andwashed with warm water. The precipitate is subsequently dried at 30° C.and 0.1 mbar for 12 h. The yield is 0.50 g (94% of theory).

1.7 Complexes of 6,3-ionene

6,3-ionene-Fluowet SB®

20 g (28% w/w, 6.1 mmol, 1.1 eq) of Fluowet SB® are introduced in 200 mlof deionized water. A solution of 1.04 g (2.8 mmol, 1 eq) ofhexadimethrine dibromide (6,3-ionene) in 50 ml of deionized water isadded slowly (1 drop per second) at a temperature of 35° C. Aprecipitate is formed which is filtered off with a Büchner tunnel,washed (with 5 times 20 ml of water conditioned at 60° C.) and dried ina vacuum drying cabinet at 30° C. and 0.1 mbar. The yield is 5.3 g (96%of theory).

6,3-ionene-Zonyl TBS®

20 g (28% w/w, 6.1 mmol, 1.1 eq) of Zonyl TBS® are introduced in 200 mlof deionized water. A solution of 1.04 g (2.8 mmol, 1 eq) ofhexadimethrine dibromide (6,3-ionene) in 50 ml of deionized water isadded slowly (1 drop per second) with stirring at a temperature of 35°C. A precipitate is formed which is immediately filtered off with aBüchner funnel, then washed (with 5 times 20 ml of water conditioned at60° C.) and dried in a vacuum drying cabinet at 30° C. and 0.1 mbar. Theyield is 5.3 g (=96% of theory).

1.8 Chitosan-Fluowet SB®

5.5 g (28% w/w, 1.7 mmol, 1.1 eq) of Fluowet SB® are introduced in 100ml of deionized water. A solution of 0.25 g of chitosan (Aldrich, lowmolecular mass) in 50 ml of 1% acetic acid is added slowly with stirring(1 drop per second) at room temperature. A precipitate is formed whichis filtered off immediately with a Büchner funnel, washed (with 3 times20 ml of water conditioned at 60° C.) and dried in a vacuum dryingcabinet at 30° C. and 0.1 mbar. The yield is 1.3 g (=91% of theory).

This complex has the particular feature that the chitosanpolyelectrolyte is obtained from biological raw materials and is fullybiodegradable. It is produced from crab shells, a waste product of thefishing industry.

1.9 Polystyrenesultonate-Hoe-L-3658-1

2.5 g (40% w/w) of the cationic surfactant Hoe-L-3658-1 are dissolved in500 ml of deionized water and the pH is adjusted to 9 using aqueoussodium hydroxide solution (10% w/w). A solution of 0.55 g ofpolystyrenesulfonate sodium salt (PSSNa, 2.7 mmol) in 100 ml ofdeionized water is added slowly (1 drop per second) with stirring at 60°C. A fine brownish precipitate is produced which is filtered off using aBüchner funnel, washed (with 3 times 20 ml of water conditioned at 60°C.) and dried in a vacuum drying cabinet at 30° C. and 0.1 mbar. Theyield is 1.4 g (=89% of theory, assuming 1.38 g ofC₆F₁₃CH₂CH₂N(CH₃)₃CH₃SO₄).

2. Preparation of Aqueous Emulsions

3.0 g of poly(trimethylammonium-propylacrylamide)-Fluowet SB® are mixedthoroughly with 20 g of liquid Fluowet OTN® (Hoechst AG). This firststep gives a homogeneous white viscous mass. In the second step, thisconcentrate is diluted in portions with water, e.g., 20, 40, 100 or 200ml. Care should be taken to ensure thorough homogenization. In thisprocess, a finely divided emulsion is obtained from the mesomorphicpowder. The proportion of emulsifier can be varied greatly. For example,as above, 6 g of complex and 10 g of emulsifier, or 12 g of complex and10 g of emulsifier, are used. All emulsions are stable at 20° C. over aperiod of at least 2 weeks.

3. Coating of an Aluminum Surface with Fluoro Complex Emulsion and theRemoval of Graffiti

An aqueous emulsion consisting of 10 g ofpoly(N,N,N-trimethylammonium-3-propylacrylamide)-Fluowet SB® complex, 10g of Fluowet OTN® solution and 40 ml of water, prepared in accordancewith Example 2) is applied by brush to a 200×200 mm aluminum panel(aluminum F22) over an area of 100×100 mm. The emulsion is dried at18-20° C. and an atmospheric humidity of 70% overnight (about 12 h). Thepanel is sprayed with a commercial acrylic paint (Auto-Color,fast-drying, color shade 6-12, Vogelsang GmbH) and the paint is curedfor 48 h. The panel was subsequently rubbed down under gentle pressurewith a solution of rinsing agent (Pril Supra, Henkel) at 30° C. using asponge (Glitzi rinsing sponge). With this treatment, the paint isdetached completely from the coated area within 30 s. On the uncoatedcomparison surface of the same panel, the paint remains adhering intact.

4. Coating of Vehicle Parts with Emulsions

An aqueous emulsion (consisting of 3 g ofpoly(N,N,N-trimethylammonium-3-propylacrylamide)-Fluowet SB® complex, 20g of Fluowet OTN® solution in 200 ml of water, prepared in accordancewith Example 2) is applied to an automobile wing using a commercial pumpatomizer and rubbed down with a cotton cloth. Under rainfall, largecoherent droplets are formed on uncoated sections of paint, whereas thewater runs off completely from the coated areas. Depending on theemulsifier content, this effect persists for varying periods of time. Inthe case of the high emulsifier concentration used in this case, theeffect disappeared gradually. After ten severe rainfalls, an effect wasno longer detectable. No alteration of the paint by the coating wasfound. It is therefore possible to prepare emulsions of the complexesfor temporary coatings of painted surfaces.

5. Coating of Painted Surfaces and the Removal of Inscriptions

An acrylic paint surface is coated uniformly using a laboratory atomizerwith 10 percent strength by weight complex solutions. After from 1 to 5minutes, a dry transparent complex film has formed on the paintedsurface. The surface energies are determined using the sessile dropmethod. In all cases, the surface energies found are below that ofTeflon (20.2 mN/m). The precise figures are given in the followingtable.

TABLE 3 Complex material Surface energy in mN/m Polyethyleneimineperfluorooctanoate 12 Poly(trimethylammonium-propyl- 16 acrylamide)perfluorooctanoate Poly(trimethylammonium-propyl- 14 acrylamide)-FluowetSB ® uncoated 57

Subsequently, all areas are inscribed using an Edding 400 permanentmarker. The inscription can be removed without problems from the coatedareas using a cotton cloth and nail varnish remover (acetone) orN-methyl-pyrrolidone, without damage to the acrylic paint. In contrastson the uncoated comparison surface, the paint starts to break upimmediately on treatment with acetone and remains adhering to the cloth.

6. Coating of an Aluminum Surface

10 ml of a two percent strength by weight alcoholic complex solution areapplied uniformly to a 200×200 mm aluminum panel using a laboratoryatomizer (Aldrich) under a pressure of 1 bar. Evaporation of the solventleaves a completely transparent film on the panel which can just be seenwith lateral incidence of light. The amount of substance used and thematerial density of approximately 1.6 g/cm³ gives a coat thickness ofabout 3 μm. Measurement of the surface energy by the sessile drop methodgives a value of about 18 mN/m (measurement with hexadecane) and istherefore considerably below the value found for polytetrafluoroethylene(20.3 mN/m). It can therefore be shown that by using even very smallamounts of substance a high-energy metal surface can be transformed veryeasily into an ultralow-energy surface. In contrast topolytetrafluoroethylene, no adhesion promoter is necessary for the coat.

7. Icing on a Coated Aluminum Surface

The prevention of ice formation on aerofoils possesses a highapplication potential in both civilian and military air travel. In thesesectors, extensive operations are necessary in the winter months inorder to de-ice the aerofoils. The icing-up of aerofoils constitutes aconsiderable safety risk in air transport. Therefore, the icing behaviorof coated aluminum plates is investigated. Coating takes place inaccordance with Example 6. In the test, a 200×200 mm aluminum plate iscooled to temperatures of −50° C. and the icing behavior is recorded.

The experimental setup consists of a 20 cm diameter Dewar flask filledwith liquid nitrogen, in which there is a solid cuboid aluminum blockwith an edge length of 15 cm. The top edge of the aluminum blockprojects 2-3 mm above the upper edge of the Dewar flask. For temperaturemeasurement, a Ni-chromium/Ni thermocouple is mounted in the center ofthe aluminum panel. The panel is placed on the aluminum block and thistime is defined as t-0. The course of icing is monitored over a periodof 2 hours. The experiment is carried out first with the uncoated plateand repeated in a second experiment with the identical but coated plate.Coating takes place in accordance with the preceding example. During theexperiment the air temperature is 19° C. and the relative atmospherichumidity is 70%.

The results are collated in the table below. The uncoated aluminum platefogs up spontaneously when it is placed on the cooled aluminum block.After just 1 minute, a clearly visible, thin layer of ice has formed. Incomparison, in the case of the coated plate there is no spontaneousfogging and after one minute no icing is observed. After 11 minutes, aconsiderable layer of ice with a thickness of 1-2 mm has already formedon the uncoated plate. At the same point in time, in the case of thecoated plate, incipient icing is found. This incipient icing iscomparable with that observed after just 1 minute in the case of theuncoated plate. After 30 minutes a coherent layer of ice is found onboth plates but with different thicknesses: in the case of the uncoatedplate its thickness is about 5-6 mm and in the case of the coated plateabout 1-2 mm. That is, it is considerably thicker in the case of theuncoated plate. Over the course of 120 minutes, the layers of ice growto thicknesses of 8-9 mm in the case of the uncoated plate and to 5-6 mmin the case of the coated plate. In this time, a total of 15 g of icehas deposited on the uncoated plate measuring 400 cm² and with a mass of100 g, whereas on the coated but otherwise identical plate only 10 g ofice were found. This experiment shows that in the case of the coatedplate a considerable delay in icing is observed. Surprisingly, thecoating has a surface structuring which greatly reduces the formation ofice nuclei.

In the second part of the experiment an attempt is made to remove theice layer formed on the plates after two hours using a coolant spray.Using the coolant spray (Super 75, Kontakt Chemie, CRC IndustriesDeutschland GmbH), which permits cooling down to −52° C., the plate issprayed front a distance of about 10 cm and thus the attempt is made toremove the ice. It is found that the adhesion of the ice on the coatedplate is greatly reduced relative to that on the uncoated plate. The icecan be removed almost completely from the coated plate by spraying withthe coolant spray, something which is not possible in the case of theuncoated plate. The ice layer at the edges of the plate cannot beremoved by simple spraying, since the plate edges are uncoated and atthe edge of the plate there is therefore strong ice adhesion as in thecase of an uncoated plate. The uncoated thermocouple lying on top of theplate also remains covered by ice. This part of the experimentdemonstrates that the adhesion of the ice layer is greatly reduced bycoating. Consequently, there is a synergistic action of the coating onicing such that both icing is retarded and the adhesion of ice which hasformed is reduced. Both effects are advantageous for reducing aerofoilicing in air travel.

TABLE 4 Time/min Plate uncoated Plate, coated  1 Temperature: −9° C.Temperature: −10° C. Plate fogs up spontaneously Plate does not fog upIcing No icing 11 Temperature: −50° C. Temperature: −52° C. Ice layerabout 1-2 mm thick Plate fogs up 30 Temperature: −55° C. Temperature:−58° C. Ice layer about 5-6 mm thick Ice layer about 1-2 mm thick 120 Temperature: −57° C. Temperature: −60° C. Ice layer about 8-9 mm thickIce layer about 5-6 mm thick

8. Coating of a Microporous Polymer Membrane

The surface modification of plastics is of great interest for aninnumerable number of very different applications. Consequently, it isinvestigated in the experiment below whether it is possible to producepore-free films on polymer surfaces with the aid of the complexesdescribed. Further underlying questions relate to the size of theamounts of substance required and to the gas permeation propertiespossessed by these films.

A suitable support material for investigating all three objectives isCelgard 2400 (Hoechst Celanese Corporation). Celgard 2400 comprisesmicroporous membrane films of polypropylene and polyethylene havingslit-shaped pores measuring 0.04×0.12 μm and having a porosity of 41%.

Coating with the complexes of the invention is effected by immersing aDIN A 4-sized Celgard 2400 film into an alcoholic solution of thecomplex. The weight fraction of the complexes is from 0.5 to 10%,preferably 2%. The Celgard film is removed from the solution and excesssolution is stripped off between two rollers. After evaporation, withdrying of the solvent, the permeabilities for the gases nitrogen, oxygenand carbon dioxide are measured at room temperature. The filmpreparation time at room temperature is from 10 to 60 minutes, typically30 minutes.

The results of gas permeation measurements can be summarized as follows:coherent impervious films are found starting from an occupation densityof from 5 to 15 g/cm². That is, all pores of the Celgard film areclosed. These films are impervious up to gas pressures of at least 5 to10 bar overpressure. The gas permeation properties show that the complexcoatings of the invention are suitable for selective gas separation. Forinstance, at 5 bar overpressure, a coating of poly(trimethylammoniumchloride-propylacrylamide)-Fluowet SB® complex (6.62 g/m²) exhibits apermeability for carbon dioxide which is 1.6 times that to nitrogen, anda permeability for oxygen which is 1.2 times higher than that fornitrogen. Likewise at 5 bar overpressure, a coating of 6,3-ionene-ZonylTBS® on Celgard (11.26 g/m²) exhibits a selectivity to carbon dioxidewhich is 1.2 times higher than that to nitrogen and a selectivity tooxygen which is 2.0 times higher than that to nitrogen.

The gas permeation measurements show that it is possible in a verysimple way co close the pores of the Celgard film with very smallamounts of substance. The films which form as a result of coatingpossess outstanding pressure stabilities. With an amount of substance offrom 5 to 10 g/m² and a density of about 1.6 g/m², the coat thicknessesare 3-6 μm. The gas permeability of the films deviates greatly from thediffusion-controlled Knudsen flow which is found for a porous material.Furthermore, the permeability can be controlled for individual gases.Poly(trimethylammonium chloride-propylacrylamide)-Fluowet SB® exhibitshigh carbon dioxide permeability while 6,3-ionene-Zonyl TBS® exhibitshigh oxygen permeability. This experiment demonstrates that stablepolymer coatings consisting of thin complex films can be produced.Furthermore, the simple preparation process, low coat thicknesses, highpressure stability, and variable selectivity to various gases suggest ahigh application potential for a great variety of gas separationprocesses.

9. Coating of Building Materials with Dissolved Complexes and theRemoval of Graffiti

Dissolved fluorinated complex material is applied using a laboratoryatomizer to plates measuring 200×200 mm made from different materials(granite, sandstone, marble). In each case, half of the plate iscovered, giving a surface region protected by complex, and anunprotected region. The drying time is from 30 to 60 minutes. After thistime, the solvent has evaporated and a transparent film has formed. Thisfilm is imperceptible or only just perceptible when viewed at an obliqueangle.

After 2 days, both the protected and the unprotected surfaces aresprayed with acrylic paint (Auto-Color, fast-drying, color shade 6-12,Vogelsang GmbH) and the paint is cured for 48 h. Subsequently, the spraycoating can be removed without residue from the coated surfaces usingnail varnish remover (acetone) or N-methyl-pyrrolidone and a papertowel. On the comparison surfaces, on the other hand, there areconsiderable paint residues remaining.

10. Coating of Paper with Dissolved Complexes and the Removal ofInscriptions

Dissolved complex material is applied using a pump atomizer to differentpapers and magazines (format: DIN A4). Evaporation of the solvent leavesa visually imperceptible film. The substrates prepared in this way aredaubed with an Edding 400 permanent marker. The daubing is removedwithout residue from the coated papers using an ethanol-soaked papertowel. On uncoated comparison material, the ink runs into the paperfibers and its removal is impossible.

11. Surface Energies of the Coatings

For quantitative detection of the change in the surface properties as aresult of coating with complexes, contact angle measurements are carriedout by the sessile drop method of Neumann and Li (J. Coll. Interf. Sci.148 (1992), 190) using the contact angle measuring instrument G10 fromKruss (Germany). From the measured contact angles, the surface energiesare calculated by the Young equation. The measurements are carried outusing hexadecane as the test liquid. For all of the complexes of theinvention set out in the synthesis examples, surface energies of between13 and 20 mN/m are found. These values are independent of the nature ofthe support material. For glass, painted metal parts, untreatedaluminum, coated paper, and sandstone, the values found are the same ineach case. From this it is possible to conclude that fluorine-containinggroups (CF₂ and CF₃) accumulate at the film/air interface in the case ofall the substrates investigated. The surface energies of typicaluncoated materials are 50 mN/m for wool, 50 mN/m for iron, 36 mN/m forpolystyrene, 23 mN/m for polydimethylsiloxane, and 20.3 mN/m forpolytetrafluoroethylene. Consequently, the values found for the coatingsare still well below those of the last two materials, which representthe standards for low-energy surfaces.

In all cases, a different but significant hysteresis between theadvancing and the receding angle is found, which depending on thematerial and the preparation conditions of the coating lies between 5and 20°. This can be explained by surface roughnesses in the microscopicrange. For polytetrafluoroethylene, the literature reports 116° (13.7mN/m) for the advancing angle and 920 (28 mN/m) for the receding angle.This gives a considerable hysteresis of 240 for polytetrafluoroethylene.Consequently, the complexes of the invention exhibit a much lowerhysteresis.

PCT/EP95/02934 describes self-cleaning surfaces based on systematicrises and dips with distance of from 5 to 200 μm and height differencesof from 5 to 100 μm. Surfaces of this kind are widespread in nature andexhibit no significant hysteresis in contact angle measurements. Owingto the structuring of the surface, the droplets of the test liquid areunable to wet the surface, since it has few, and small, areas of contactwith the substrate. In the case of fluorosurfactant complexes describedhere, the hystereses found are clear evidence that no such surfacestructuring is present.

12. Characterization of the Surfaces by EX and EDX Analysis

A film of the poly(trimethylammonium chloridepropylacrylamide)-FluowetSB® complex is cooled for 2 minutes in liquid nitrogen, the film thusembrittled is fractionated, and the fractured edge is imaged in thescanning electron microscope (SEM). The top image in FIG. 1 shows afracture edge of this kind at an acceleration voltage of 20 kV and amagnification of 5000. The light-colored fracture edge and the filmsurface, which appears dark, are readily perceptible. The rounded-offfracture edge in the left-hand half of the image possesses a diameter ofabout 5 μm.

The film is subsequently analyzed by EDX (energy dispersed X-ray)specifically for the presence of fluorine (F_(κα)=0.2675 keV). Themeasurement of the same fracture edge as in the SEM micrograph is shownin the bottom image in FIG. 1. The light-colored spots are classified asregions of high fluorine content. It is noted that the film surfacewhich appears dark in the SEM is covered by numerous spots whereas thefracture edge which appears light-colored in the SEM has only a few suchspots. This means that the surface is greatly enriched in fluorinerelative to the bulk material and the fluorine groups (CF₂ and CF₃) arethus in fact, as is preferred, located on the film surface.

13. Comparison of Surface Energy and Water Absorption

For the usefulness of the coating materials in the architectural sector,it is important that they do not give a watertight seal to the surfaces.They must, therefore, be able to absorb water. If, however, they absorbtoo much water and swell too severely, then they are likewise unusable.It is therefore necessary to be able to control the water absorption.Using the example of the complexes of perfluorodecanoic acid with thecopolymers of diallyldimethylammonium chloride (DADMAC) and ofN-methylvinylacetamide (NMVA), the intention is to demonstrate the veryconsiderable extent to which it is possible to vary the water absorptioncapacity for an approximately constant surface energy. This is done withthe same surfactant, the perfluorinated decanoic acid, by altering thecopolymer composition. The water absorption of these complexes at 20° C.and 100% relative atmospheric humidity increases with increasing DADMACcontent from 1.4% (25%DADMAC) to 6.1 (99% DADMAC).

TABLE 5 DADMAC/NMVA Water absorption [%] Surface energy [mN/m] 25:75 1.414.0 47:63 3.6 13.5 65:35 3.8 14.6 83:17 4.8 14.7 100:0  6.3 15.6

14. Small-angle X-ray Scattering

All of the complexes investigated are analyzed by means of small-angleX-ray scattering. It is found that in each case the structure presentresembles that of a liquid crystal. This is evident from small-anglereflections which correspond to a Bragg spacing of between 1 and 100 nm.In this respect, the behavior of the fluorinated complexes is similar tothat of the nonfluorinated complexes described in DE 4428641. In thatcase, however, it is emphasized that following precipitation fromaqueous solution the complexes are amorphous (no small-anglereflections). They are then dissolved in an organic solvent and, in athird step, are filmed. In that case, again, it is especially emphasizedthat a mesomorphic order is present only after filming from organicsolvent (small-angle reflections occur).

In the case of fluorinated complexes, in contrast, we find the samesmall-angle reflections both following precipitation from aqueoussolution and following filming from an organic solvent; in other words,a mesomorphic structure is present directly in the aqueous medium asearly as at the complexing stage.

15. Wide-angle X-ray Scattering

The coatings only possess high transparency when they do not possesscrystallinity. This can be found very rapidly and easily by means ofwide-angle X-ray measurements.

In the case of the complexes of the invention, only a few broadreflections are found. Typically, an intense reflection is found atabout 1.9 nm⁻¹ and a weaker reflection at about 4.2 nm¹ (see FIG. 2). Assoon as crystallinity occurs, a number of, or numerous, narrowreflections are found in the wide-angle diffractogram. In the regionaround 2 nm⁻¹ at least two sharp reflections can be observed. This isillustrated in FIG. 3. The diffractogram 3 d shows a complex which isstill among the complexes of the invention. It possesses only one,albeit narrow, reflection around 2 nm⁻¹. In the diffractogram 3 e, anumber of reflections can be observed within this region. In otherwords, the complex is crystalline and is no longer one of the complexesof the invention.

In addition to clear analysis, the wide-angle x-ray diffractograms alsomake it possible to demonstrate the effect of the copolymers on thestructure. The diffractograms 2 a to c, and 3 d, relate topoly(diallyldimethylammonium-co-N-methyl-N-vinylacetamide)perfluorodecanoate (see syntheses). The diallyldimethylamonium contentof the copolymers is 25% (a), 47% (b), 65% (c), and 83% (d). Thewide-angle diffractograms demonstrate that all of the complexescontaining copolymer do not possess any crystallinity. The homopolymericpoly(diallyldimethylammonium) perfluorodecanoate (3 e), on the otherhand, is crystalline, or at least possesses considerable crystallinefractions.

What is claimed is:
 1. A complex comprising at least one nonhygroscopicpolyelectrolyte and at least one oppositely charged fluorinatedsurfactant.
 2. The complex as claimed in claim 1, whose stoichiometrybased on the charges of polyelectrolyte and surfactant is about 1:1. 3.The complex as claimed in claim 1, which comprises a cationicpolyelectrolyte and an anionic surfactant.
 4. The complex as claimed inclaim 1, which comprises an anionic polyelectrolyte and a cationicsurfactant.
 5. The complex as claimed in claim 1, which has a waterabsorption of not more than 5% (w/w), based on the weight of thecomplex, at 20° C. and 100% relative atmospheric humidity.
 6. Thecomplex as claimed in claim 1, comprising a nonhygroscopic cationicpolyelectrolyte selected from the group consisting of polymerscontaining at least one monomer unit selected from ethylenicallyunsaturated monomers which carry positively charged nitrogen groups,polyethyleneimines and alkyl-substituted polyethyleneimines; ionenes,and polysaccharides containing cationic groups.
 7. The complex asclaimed in claim 6, wherein said cationic polyelectrolyte comprises atleast one monomer unit which carries a quaternary ammonium group or anN-substituted heteroaromatic group.
 8. The complex as claimed in claim6, wherein said cationic polyelectrolyte further comprises nonionicmonomer units.
 9. The complex as claimed in claim 6, wherein saidcationic polyelectrolyte comprises a copolymer ofdialkenyldialkylammonium salts and nonionic monomers.
 10. The complex asclaimed in claim 1, comprising a nonhygroscopic anionic polyelectrolyteselected from the group consisting of: polymers containing at least onemonomer unit selected from ethylenically unsaturated carboxylic acidsand also salts and derivatives thereof, ethylenically unsaturatedmonomers containing sulfonic acid groups, and ethylenically unsaturatedmonomers containing phosphinic, phosphonic or phosphoric acid groups,and anionic polysaccharides.
 11. The complex as claimed in claim 10,wherein said anionic polyelectrolyte further comprises nonionic monomerunits.
 12. The complex as claimed in claim 1, comprising an anionicfluorinated surfactant selected from the group consisting of:fluorinated carboxylic acids, fluorinated sulfonic acids, fluorinatedorganosulfuric acids, fluorinated phosphinic, phosphonic andorganophosphoric acids, and anionic derivatives or salts thereof. 13.The complex as claimed in claim 12, wherein said anionic fluorinatedsurfactant is selected from the group consisting of: perfluorocarboxylicacids and salts thereof; partially fluorinated carboxylic acids andsalts thereof; perfluorosultonic acids and salts thereof; partiallyfluorinated sulfonic acids and salts thereof; fluorinated phosphinic andphosphoric acids and salts thereof; fluorinated phosphoric acids andsalts thereof, and fluorinated esters which carry at least one chargedgroup.
 14. The complex as claimed in claim 1, comprising a cationicfluorinated surfactant selected from fluorinated amines and ammoniumsalts.
 15. The complex as claimed in claim 1, which further comprises atleast one nonionic surfactant.
 16. The complex as claimed in claim 15,which comprises at least one nonionic fluorinated surfactant.
 17. Thecomplex as claimed in claim 15, which comprises said nonionic surfactantin a proportion of up to 200% (w/w) based on the weight of the complex.18. A method of preparing a complex as claimed in claim 1, whichcomprises adding an aqueous solution of the polyelectrolyte to anaqueous solution of the fluorinated surfactant and isolating theresultant precipitate.
 19. A method of preparing a complex, whichcomprises adding the particular desired amount of nonionic surfactant toa complex as claimed in any of claims 1 to
 7. 20. A formulation whichcomprises a complex as claimed in claim 1, in solution in a polarorganic solvent.
 21. The formulation as claimed in claim 20, whereinsaid solvent is selected from methanol, ethanol, acetone, ethyl acetate,and mixtures thereof.
 22. The formulation as claimed in claim 20,wherein said complex is present in a proportion of from 0.1 to 30% (w/w)based on the weight of the solution.
 23. A formulation which comprises acomplex as claimed in claim 1 in emulsion in an aqueous solvent.
 24. Theformulation as claimed in claim 23, wherein said complex is present in aproportion of from 0.1 to 30% (w/w) based on the weight of the emulsion.25. The formulation in claim 24, wherein said emulsion is stable for atleast two weeks at 20° C.
 26. A method of preparing a formulation; whichcomprises adding the particular desired amount of a nonionic surfactantto a complex as claimed in any of claims 1 to 7, converting theresulting mixture into a substantially homogeneous mixture, and dilutingthe mixture with water in order to obtain an aqueous emulsion.
 27. Amethod of coating a surface, which comprises applying to said surface aformulation as claimed in claim 25 and drying it.
 28. The method asclaimed in claim 27, wherein said applying takes place from a solution.29. The method as claimed in claim 27, wherein said applying takes placefrom an aqueous emulsion.
 30. The method as claimed in claim 27, whereinsaid applying takes place discontinuously or continuously by spraying,flow coating, dipping or mechanical application.
 31. The method asclaimed in claim 27, wherein the coating is applied in a thickness offrom 0.1 μm to 1 mm.
 32. The method as claimed in claim 28, wherein thedrying time is not more than 1 hour.
 33. The method as claimed in claim29, wherein the drying time is not more than 6 hours.
 34. An articlewhich is coated at least in part with a complex as claimed in claim 1.35. The article as claimed in claim 34, wherein the coated surface hasan energy of less than 20 mN/m.
 36. The article as claimed in claim 35,wherein the coating is substantially transparent.
 37. The article asclaimed in claim 34, wherein the coating is permeable to air and/ormoisture.
 38. The article as claimed in claim 34, wherein the coating isstable on contact with a water-containing atmosphere.
 39. The article asclaimed in claim 34, wherein the coating is stable up to a temperatureof 100° C.
 40. The article as claimed in claim 34, wherein the coatingis enriched with fluorine at the surface facing the surroundings. 41.The article as claimed in claim 34, wherein the coating has a waterabsorption of not more than 5% (w/w), based on the weight of thecomplex, at 20° C. and 100% relative atmospheric humidity.
 42. A complexcomprising at least one polyelectrolyte, at least one oppositely chargedfluorinated surfactant and at least one non-ionic surfactant.
 43. Amethod of preparing the complex of claim 42, comprising adding anaqueous solution of the polyelectrolyte to an aqueous solution of thefluorinated surfactant and isolating the resultant precipitate.
 44. Amethod of preparing a complex comprising at least one polyelectrolyte,at least one oppositely charged fluorinated surfactant and at least onenonionic surfactant comprising adding an nonionic surfactant to acomplex comprising at least one polyelectrolyte and at least oneoppositely charged fluorinated surfactant.
 45. A formulation whichcomprises the complex of claim 42 in solution in a polar organicsolvent.
 46. A formulation which comprises complex comprising at leastone polyelectrolyte and at least one oppositely charged fluorinatedsurfactant in emulsion in an aqueous solvent.
 47. A method of preparinga formulation comprising adding an nonionic surfactant to a complexcomprising at least one polyelectrolyte and at least one oppositelycharged fluorinated surfactant, converting the resulting mixture into asubstantially homogeneous mixture, and diluting the mixture with waterin order to obtain an aqueous emulsion.
 48. An article having a surfacecoated with the complex of claim
 42. 49. A method of coating a surfacecomprising coating a surface with the complex of claim 42.